I have yet to meet a climate scientist who does not believe that global warming is a worse problem than they thought a few years ago. The seriousness of this change is not appreciated by politicians and the public. The scientific world carefully measures the speed with which we approach the cliff and will, no doubt, carefully measure our rate of fall. But it is not doing enough to stop it. I am a specialist in investment bubbles, not climate science. But the effects of climate change can only exacerbate the ecological trouble I see reflected in the financial markets — soaring commodity prices and impending shortages.

One of the most urgent aspects of this impending crisis is the shrinking supply of fertilizer, most of which comes from just three parts of the world.

Then there is the impending shortage of two fertilizers: phosphorus (phosphate) and potassium (potash). These two elements cannot be made, cannot be substituted, are necessary to grow all life forms, and are mined and depleted. It’s a scary set of statements. Former Soviet states and Canada have more than 70% of the potash. Morocco has 85% of all high-grade phosphates. It is the most important quasi-monopoly in economic history.

"What happens when these fertilizers run out is a question I can’t get satisfactorily answered and, believe me, I have tried," he writes. "There seems to be only one conclusion: their use must be drastically reduced in the next 20–40 years or we will begin to starve."